High-Field Electron Transport and High Saturation Velocity in Multilayer Indium Selenide Transistors

Creating a high-frequency electron system demands a high saturation velocity (υsat). Herein, we report the high-field transport properties of multilayer van der Waals (vdW) indium selenide (InSe). The InSe is on a hexagonal boron nitride substrate and encapsulated by a thin, noncontinuous In layer, resulting in an impressive electron mobility reaching 2600 cm2/(V s) at room temperature. The high-mobility InSe achieves υsat exceeding 2 × 107 cm/s, which is superior to those of other gapped vdW semiconductors, and exhibits a 50–60% improvement in υsat when cooled to 80 K. The temperature dependence of υsat suggests an optical phonon energy (ℏωop) for InSe in the range of 23–27 meV, previously reported values for InSe. It is also notable that the measured υsat values exceed what is expected according to the optical phonon emission model due to weak electron–phonon scattering. The superior υsat of our InSe, despite its relatively small ℏωop, reveals its potential for high-frequency electronics, including applications to control cryogenic quantum computers in close proximity.